Neodymium doped acetate glass exhibiting fluorescence at 1.06 micrometers

ABSTRACT

A novel glass exhibits fluorescence from trivalent neodymium ions at a wavelength of approximately 1.06 micrometers. The glass consists essentially of about 6 weight percent of Nd(C2H3O2)3 and about 94 weight percent of a host glass selected from a group consisting of NaC2H3O2, Pb(C2H3O2)2, KC2H3O2, Ca(C2H3O2)2, and combinations thereof where the Nd(C2H3O2)3 contributes trivalent neodymium ions to the glass.

United States Patent [191 Shaw et al.

[451 Mar. 4, 1975 NEODYMIUM DOPED ACETATE GLASS EXHIBITING FLUORESCENCE AT 1.06 MICROMETERS [75] Inventors: Robert R. Shaw, Sturbridge; Elias Snitzer, Wellesley, both of Mass.

[73] Assignee: American Optical Corporation,

Southbridge, Mass.

22 Filed: Jan. 11, 1973 [21] Appl. No.; 322,679

[52] U.S. Cl..... 252/3013 R, 106/47 Q, 331/945 E [51] Int. Cl C09k 1/02, C03c 3/28, C03c 3/12 [58] Field of Search 106/47 R; 252/3013 R [56] References Cited UNITED STATES PATENTS 3,549,554 12/1970 Hirayama et a1 106/47 R 3.649551 3/1972 Bartholomew 106/47 R OTHER PUBLICATIONS Bartholomew et aL-J. Amer. Cer. Soc., 52(7),.luly 1,

1969, "Vitreous Nature of Some New Inorganic Glasses as shown by X-ray Diffraction, p, 402.

Primary E.ranzinerWinston A. Douglas Assistant E.\'aminerMark Bell Attorney, Agent, or FirmWilliatn C. Nealon [57] ABSTRACT 4 Claims, 1 Drawing Figure /OOO PATENTEDHAR 4 915 RELATIVE INTENSITY WAVELENGTH IN NHNOMETERS NEODYMIUM DOPED ACETATE GLASS EXHIBITING FLUORESCENCE AT 1.06 MICROMETERS BACKGROUND OF THE INVENTION This invention is related to novel glasses and is more particularly concerned with such glasses which exhibit fluorescence when doped with trivalent neodymium ions.

In recent years, the glass laser has become an extremely important class of lasers. The glasses are doped generally with trivalent rare earth ions. Predominant among these rare earth laser ions is the neodymium ion. Glass lasers doped with trivalent neodymium ions are capable of generating very high power outputs at relatively high efficiencies.

Glass has various characteristics which make it an ideal laser host material. It can be made in large pieces of diffraction-limited optical quality, e.g. with an index of refraction variation of less than 1 part per million across a 2.5 centimeter diameter. In addition, glass lasers have been made in a variety of shapes and sizes from fibers of a few microns diameter supporting only a single dielectric waveguide mode, to rods which are 2 meters long and 7.5 centimeters in diameter. Further more, pieces of glass with quite different optical properties can be fused to solve certain system design problems. For example, glass compositions can be varied in order to acquire an index of refraction varying throughout the range of from 1.5 to 2.0. Therefore, those skilled in the art are constantly searching for new glassy materials which can serve as viable hosts for the trivalent neodymium laser ions. This is done in order to enlarge the spectrum of physical, optical, and chemical properties required in order to provide a glass laser material totally compatible with the designers system requirements.

When searching for such viable host materials, it is characteristic to examine the fluorescence spectrum exhibited by the hostmaterial when doped with the trivalent neodymium ions. When one acquires such a host material, it is highly probable than an operable laser material can be formed of the new glass. The limitations on this generally revolve around the ability to manufacture the glass in sufficient quantity and of sufficient optical quality.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide novel laser materials which exhibit fluorescence at the characteristic wavelength, 1.06 micrometers, generally associated with the trivalent neodymium ion.

Briefly, the invention in its broadest aspect comprises an acetate glass consisting essentially of about 6 weight percent of Nd(C H O in a host glass selected from a group consisting of Pb(C H O KC H O Ca(C H O NaC H O and combinations thereof, the Nd(C H O contributing trivalent neodymium ions to the glass.

Further objects, advantages, and features of the invention will be apparent from the following detailed description of the invention.

DESCRIPTION OF THE DRAWING In the drawing, the sole FIGURE is a graphical representation of a typical fluorescence spectrum of a glass according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, a typical fluorescence spectrum curve is shown. The curve shows two peaks, at approximately 1.06 micrometers and at approximately 0.9 micrometers. The peak at 1.06 micrometers is generally the most important in glasses doped with neodymium. The peaks have relative intensity values A and B, associated with the peaks at 0.9 and 1.06 micrometers, respectively.

The fluorescence curves shown were measured in a Cary 14 spectrophotometer by placing the glass samples in a copper fixture which in turn were placed in the sample compartment of the Cary. The glass was irradiated at right angles with a Xenon arc lamp through a filter which blocked the transmission of wavelengths longer than approximately 800 nm. The fluorescent spectrum was recorded using the automatic slit control which adjusted the slit width so that the. output of a coiled tungsten filament lamp with a filament temperature of approximately 2800K produced a constant deflection on the recording chart for all wavelengths. Thus the recording chart must be corrected to obtain the true relative intensities by dividing the chart deflec tion by a factor proportional to the energy radiated by the tungsten lamp at the wavelengths of interest. We have estimated the correction factor to be approximately unity at the wavelengths of interest. This estimate was made by using the tungsten emissivities measured by J. C. DeVos (J. C. DeVos, Physics 20,690 (1954) for a ribbon filament tungsten lamp operating at 2800K in a calculation of the energy radiated by the coiled filament lamp at the two wavelengths of interest. The intensity ratios reported here were measured directly from the Cary charts using no correction factor.

Several examples of glasses according to the present invention are given in the following examples. Each of these glasses was formed in approximately a 50 gram melt. The glass is preferably formed in the following manner. The components were added to the batch as Nd(C2H302)'3H20, NaC2H302 Pb(C2H302)2'3H20, KC l-I O and Ca(C H O 'H O.. The constituents were added in the known stoichiometric amounts to yield a glass having a final composition as given in the following examples. The glass making materials must be of high purity and, in particular, must be free of contamination from iron or other elements which would cause light absorption at the primary fluorescence wavelength, 1.06 micrometers, if present in the glass. The finished glass, for example, should not contain more than 5 parts per million of iron as Fe O The glass may be prepared by fusing the raw materials in a Pyrex crucible heated in a Globar electric furnace, an RF induction coil, or a gas flame. No special atmosphere was necessary in the furnace. The raw materials were mixed intimately and as completely as possible in a mixing device that does not introduce any contamination. The mixed batch was loaded into a Pyrex crucible which did not contaminate the melt with undesired impurities. The crucible was raised to a melting temperature of 300C. The batch was held at this temperature for approximately 15 minutes for the 50 gram samples. During this time, the melt was stirred with a platinum rod. The glass was then cast onto an iron plate at room temperature. It is to be understood that larger samples require a different procedure.

EXAMPLE 1 A glass which consists of about 94 weight percent of a host glass and about 6 weight percent of Nd(C H O has values for A and B of 0.04 and 0.13 respectively on the fluorescent emission spectrum. The composition, in mol percent, of the host glass is essentially NaC H O 33.3 z a z 33.3 2 a 2)2 33.3

EXAMPLE 2 A glass which consists of about 94 weight percent of a host glass and about 6 weight percent of Nd(C l-l O has values for A and B of 0.45 and 0.09 respectively on the fluorescent emission spectrum. The composition, in mol percent, of the host glass is essentially itc n o so Pb(C H O 50 EXAMPLE 3 characteristics thereof. The present embodimentsare therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embranced therein.

What is claimed is:

1. An acetate glass which exhibits fluorescence at a wavelength of 1.06 um consisting essentially of about 6 weight percent of Nd(C H O in a host glass selected from a group consisting of Pb(C H -,O KC H O NaC H O Ca(C H O and combinations thereof, the Nd(C H O contributing trivalent neodymium ions to the glass.

2. An acetate glass according to claim 1, wherein the host glass has essentially the following composition as given in mol percent.

Nac H o 33. 3 KC H O 3 3 .3 2 a 2)2 33.3

3. An acetate glass according to claim 1, wherein the host glass has essentially the following composition as given in mol percent.

4. An acetate glass according to claim 1, wherein the host glass is Pb(C H;,O 

1. AN ACETATE GLASS WHICH EXHIBITS FLUORESCENCE AT A WAVELENGTH OF 1.06 UM CONSISTING ESSENTIALLY OF ABOUT 6 WEIGHT PERCENT OF ND(C2H3O2)2, KC2H3O2, THE ND(C2H3O2)3 CONCONSISTING OF PB(C2H3O2)2, KC2H3O2, NAC2H3O2, CA(C2H3O2)2, AND COMBINATIONS THEREOF, THE ND(C2H3O2)3 CONTRIBUTING TRIVALENT NEODYMIUM IONS TO THE GLASS.
 2. An acetate glass according to claim 1, wherein the host glass has essentially the following composition as given in mol percent.
 3. An acetate glass according to claim 1, wherein the host glass has essentially the following composition as given in mol percent.
 4. An acetate glass according to claim 1, wherein the host glass is Pb(C2H3O2)2. 